The present invention relates generally to refrigerant circuit control apparatus and methods, and, in a representatively illustrated embodiment thereof, more particularly provides specially designed apparatus and methods for controlling an electronic expansion valve in a heat pump refrigerant circuit.
In previously proposed control systems for controlling an electronic expansion valve in a refrigerant circuit, it was necessary to transmit multiple output signals from a unit control to an expansion valve control, such multiple output signals representing a variety of system and component operating characteristics representatively including (1) a first stage compressor operation signal, (2) a second stage compressor operation signal, (3) a heat pump heating mode signal (as determined by a reversing valve position signal), (4) a heat pump cooling mode signal (as determined by a reversing valve position signal), and (5) a defrost mode signal. Multiple corresponding operational characteristic and mode inputs of various types also had to be constructed and connected to the unit control. These previous necessities undesirably increased the complexity and cost of the unit control and thus the overall complexity of the overall air conditioning system, due to the additional structure and signal generating capability required to be incorporated in the unit control.
As can be readily seen from the foregoing, a need exists for simpler, less complex, and less expensive apparatus and methods for controlling an electronic expansion valve in an air conditioning system such as a heat pump system.